There was a long-running controversy about whether the Kea preys on sheep. Sheep suffering from unusual wounds on their sides or loin were noticed by the mid-1860s, within a decade of sheep farmers moving into the high country. Although some supposed the cause was a new disease, suspicion soon fell on the Kea. James MacDonald, head shepherd at Wanaka Station, witnessed a Kea attacking a sheep in 1868, and similar accounts were widespread. Prominent members of the scientific community accepted that Kea attacked sheep, with Alfred Wallace citing this as an example of behavioural change in his 1889 book Darwinism. Despite substantial anecdotal evidence of these attacks, In 1993, however, its nocturnal assaults were captured on video, proving that at least some Kea will attack and feed on healthy sheep. The video confirmed what many scientists had long suspected, that the Kea uses its powerful curved beak and claws to rip through the layer of wool and eat the fat from the back of the animal. Though the bird does not directly kill the sheep, death can result from blood poisoning or accidents suffered by animals trying to escape.